Preheat grill. Remove stems from eggplants and slice on a slant into 1/2-inch slices. Core, seed and quarter the pepper. Remove stems from zucchini and cut lengthwise into 4 long slices. Using 1 tablespoon oil, brush vegetables very lightly, then grill until browned on both sides. Set aside until cool enough to handle.

Heat peanut oil in a large skillet. Add onion, ginger and garlic and cook over medium-low heat until tender, about 5 minutes. Dice grilled vegetables into 1/2-inch cubes, adding to skillet as you chop. Add tomato and cook, stirring gently with a wooden spoon, about 5 minutes. Add oyster sauce, rice vinegar and sesame oil. Stir and continue cooking 2 to 3 minutes longer. Season to taste with salt and pepper and stir in green onions. Sprinkle with cilantro and serve hot or at room temperature.